Too many firewalls?

Hi,
i'm completely new to home networking and would like some help, please.
i'm helping someone to setup home office- with 3- 4pcs, 1 'server'. all
pcs & server have xp sp2, norton internet security (build in firewall),
and connect to dsl line using 1 router/ gateway (build in firewall).
however, they also already bought a cisco pix 501 firewall a while ago
(they used vpn before).
i'm just wondering should i set that firewall too? if i do that, would
it be a bit too much?
the router only have 4 ports. at the moment, i only use 1 socket to
connect to the router. can use their existing dsl 300+ on another
socket (they have 4 sockets), but will it stop the pcs from seeing each
other on the network?
if i can't use this socket (if it stops it from seeing each other), why
the supplier install 4 sockets? i guess it probably means they can use
4 routers?
when i try to map a drive to the 'server' (not a proper server, just
microsoft windows, to act as a server), it won't show the other pcs on
the 'network' although they are all on the same workgroup. i can only
map it using ip address. any idea? i thought it could be the firewall
(router) and changed the firewall settings to allow all applications,
but still can't see it. any idea?
thanks
Received on Mon Nov 21 02:41:30 2005